1. Field of the Invention
The present invention resides in a catalyst comprising a zeolite dispersed in an alumina-aluminum phosphate-silica matrix suitable for use in a process for increasing gasoline yield and quality.
Around the turn of the century, motor vehicles in the United States began to appear in increasing numbers and gasoline obtained a degree of marketable value as a refinery product. Shortly thereafter, demand in the United States for motor fuels began to exceed the amount produced from refinery crude-oil runs geared for producing kerosene, fuel oils, etc., which were very much in demand at the time. Since then the petroleum industry's most prominent problem has been inventing new and more efficient methods to meet the tremendous demand for gasoline without overproducing other petroleum products at the same time.
Due to the continually increasing demand for gasoline and the ever-shrinking supplies of crude cracking stocks, such as gas oils and the like, more attention has recently been directed to the catalytic cracking of heavier charge stocks such as petroleum residuals. These charge stocks, however, suffer from the disadvantage of having high metals content which is concentrated therein during a normal cracking process. The metals tend to deposit on catalysts and decrease the cracking characteristics thereof in a cracking process. The novel catalysts defined and claimed herein are particularly formulated to increase the gasoline yield and quality (i.e., BTX) from gas oils during a cracking process and additionally to catalytically crack petroleum residuals with high selectivity to gasoline production as well as having improved metals tolerant characteristics. Examples of typical metals which can be present during the cracking process include the following: nickel, vanadium, copper, chromium and iron.
2. Description of the Prior Art
The use of zeolitic cracking catalysts has become of increased importance in petroleum cracking processes due to the higher activity characteristics of these catalysts (see "Recycle Rates Reflect FCC Advances", by J. A. Montgomery, Oil & Gas Journal, Dec. 11, 1972, pp 81-86).
Several processes have been proposed in the past wherein zeolite catalysts are utilized to crack crude oils and petroleum residual feedstocks. One such process is set forth in U.S. Pat. No. 3,944,482; entitled "Process for the Cracking of High Metals Content Feedstocks", issued to Mitchell et al, on Mar. 16, 1976. The reference discloses the use of a zeolite catalyst dispersed with a large pore matrix, for example, alumina, alumina silicate clay, etc., in a process to crack high metals content feedstocks. Although zeolites are disclosed, the particular combination of zeolite composited with an alumina-aluminum phosphate-silica matrix, as specifically defined herein, to increase gasoline production in a cracking process is not appreciated.
U.S. Pat. No. 3,835,032, entitled "Catalytic Cracking with Silver-Rare Earth or Copper-Rare Earth Exchanged Y-Type Zeolite", issued to Dolbear et al, on Sept. 10, 1974, relates to a zeolite hydrocarbon cracking catalyst which consists of synthetic Y-type zeolite exchanged with silver or copper ions in combination with rare earth ions. The exchanged zeolite is combined with an inorganic oxide matrix, for example, inorganic hydrogels, such as silica, alumina and silica-alumina hydrogel. These catalysts are described as capable of producing a high yield of aromatic gasoline fractions of enhanced octane rating.
Another hydrocarbon cracking zeolite catalyst is disclosed in U.S. Pat. No. 3,985,640, entitled "Cracking with Zeolite Catalysts Promoted with Uranium or Uranium Plus Silver", issued to Lussier et al, on Oct. 12, 1976. Particularly, the reference relates to zeolite promoted hydrocracking catalysts consisting of a type X or Y faujasite zeolite exchanged with uranium or uranium in combination with silver ions dispersed on a kaolin clay, amorphous silica alumina matrix. The catalyst is said to be highly active and selective for the production of gasoline from gas oils.
High surface area aluminum phosphate gels, methods of making and using them as catalysts or catalyst supports are disclosed in U.S. Pat. No. 3,342,750; entitled "Compositions Containing Stable Aluminum Phosphate Gel and Methods of Making and Using Same; issued to Kearby, on Sept. 19, 1967. In particular, the reference relates to the preparation of aluminum phosphate gels, in a preferred mode, by reacting ethylene oxide with a cold aqueous solution of aluminum chloride and phosphoric acid. The aluminum phosphate gels are next calcined and used as catalysts or supports in a hydrocarbon cracking process.
U.S. Pat. No. 3,904,550, entitled "Hydrocarbon Conversion Catalyst Comprising Alumina and Aluminum Phosphate", issued to Pine, on Sept. 9, 1975, discloses a catalyst support consisting of alumina and aluminum phosphate which is prepared by reacting an aluminum alkoxide with an aqueous solution containing phosphate ions. The product is recovered and calcinated, which in turn can be combined with various known catalyst components, for example, zeolites, to produce a hydrocarbon cracking or desulfurization and denitrogenation catalyst. It is to be noted that the above-cited references fail to appreciate a catalyst system comprising zeolite composited with an alumina-aluminum phosphate-silica matrix, as specifically defined herein, to increase gasoline production and quality in a hydrocarbon cracking process.